OBJECTIVES

MATTER

EVALUATION

HEAT

Standard competency and Basic Competency

STANDARD COMPETENCY

Describe role of heat in changes

states of matter and temperature’s substance also its application in daily life

: Comprehending states of matter and its

change

HEAT

BASIC COMPETENCY

ARE HEAT ENERGY AND TEMPERATURE JUST THE SAME THING?NO! LET'S GET THIS CLEAR:

HEAT IS THE ENERGY STORED INSIDE SOMETHING.TEMPERATURE IS A MEASUREMENT OF HOW HOT OR COLDSOMETHING IS.

AN OBJECT'S TEMPERATURE DOESN'T TELL US HOW MUCH HEATENERGY IT HAS.

HEAT AND TEMPERATURE

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• Before the 9th century, many scientistbelieved that heat was a fluid.

• Heat as fluid firstly stated by AntoineLaurent Lavoisier, He said that when ahotter object was in contact with thecolder object, then the fluid would flow

• Some scientist disagreed with the conceptof Heat as fluid. Those scientist proved that

Heat was not a fluid, but a form of Energy Antoine Lavoiser

HISTORY OF HEAT

Heat energy is the total energy of particles composing amatter.

Heat is one form of energy which is flowing from an object withhigher temperature to another object with lower temperature

The unit of Heat is Joule (J)Heat is also expressed in units of calories.

One calorie defined as the amount of heat needed to heat 1

gram of water until its temperature increasing 1 C °.1 calorie = 4.2 joules1 joule = 0.24 calories

6What Is Heat?

Heat Transfer

• Heat always moves from a warmer place to a cooler place.

• Hot objects in a cooler room will cool to room temperature.e.g: tea, coffee

• Cold objects in a warmer room will heat up to room temperature.e.g: butter, ice

What do you think?

Forms of Heat Transfer

Heat

Tran

sfer

Conduction

Convection

Radiation

RadiationHow does heat energy get from the Sun to the Earth?

There are no particles between the Sun and the Earth so it MUST travel by radiation

?RADIATION

Radiation

• The transfer of heat in rays, from a hot object, without needing a medium to pass through

• It travels in all directions from a hot object

• The hotter an object is, the more heat it will radiate out

• Does the surface affect the way heat is radiated?

What colour should we paint radiators?Which colour is better to wear on a sunny day?black or white?

• A dull black surface will radiate and absorb heat better than a bright shiny surface.

Four containers were filled with warm water. Which container would have the warmest water after ten minutes?

Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.

shiny metal

radiationdull black

emitting

Radiation – Think Pair-ShareRadiation travels in straight lines

True/False

Radiation can travel through a vacuum

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False

Radiation questions

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.Why are shiny foil blankets wrapped around marathon runners at the end of a race?

The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold.

Conduction• Transfer of heat is through a SOLID by

being passed from one particle to the next• Particles at the warm end move faster and

this then causes the next particles to move faster and so on. e.g: poker in fire

spoon in tea• In this way heat in an object travels from:

the HOT end the cold end

Conduction• When you heat a metal strip at one end, the heat travels to

the other end.

• As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

Conductors/Insulators

• If a substance easily allows heat to move through it, we can say it is a good conductor of heat. e.g: most metals

• If a substance does not allow heat to pass through it easily we can say it is an Insulator. E.g: wood, plastic, glass

• Why do many sauce pans have plastic handles?

Conduction V Insulation

Conductor or Insulator?• Wood?• Aluminium?• Plastic?• Glass?• Iron?• Polystyrene?• Copper?• Cardboard?

ConvectionWhat happens to the particles in a liquid or a gas when you heat them?

The particles spread out and become less dense.

A liquid or gas.

Convection• It is the way in which

particles in a GAS or LIQUID move upwards, carrying heat with them

• Think about when you boil water, the bubbles move upwards

• Or think of a gas heater in the room, the heat rises around the room

Convection

Hot water rises

Cooler water sinks

Convection current

Cools at the surface

ConvectionWhere is the

cooling compartment

put in a fridge?

Cooling compartment

It is put at the top, because cool air sinks, so it cools the food on the way down.

It is warmer at the bottom, so this warmer air rises and a convection current is set up.

Should a radiator be called a radiator?

Convection questions

Why are boilers placed beneath hot water tanks in people’s homes?

Hot water rises.

So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

Why does hot air rise and cold air sink?Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.

of temperatureHeat and the change

Not all substances have the same ability in absorbingheat.

The ability to absorb heat determined by the nature ofa substance called specific het capacity.

Specific Heat Capacity (c)The specific heat capacity of a substance is

defined as the heat required to raising thetemperature of 1 kg of the substance by 1°C.

The unit of specific heat capacity is joule per kilogramper Celsius degree (J/kg C°)

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This proved that heat needed to raise thetemperature of 1C ° alcohol is smallerthan the heat needed to raise watertemperature at 1C°. That is, alcohol heatfaster than water.

8Specifik Heat Capacity

The amount of heat (Q) required by an object is proportional tothe mass of the object (m), depending on the specific heat capacity(c), and comparable to the increase in temperature(∆T).

The change of heat (received heat or released heat) of asubstance cannot be measured directly, but it can be calculatedusing the following equation.

Q = m x c x ΔTNotes:Q = heat received or released (Joules)m = mass (kg)c = specific heat capacity (J/kg C°)ΔT = changes of temperature (C°)

9

Calculati ng Heat

ExampleCalculate heat needed to increasing temperature of 500 gwater from 20 ° C to 100 ° C,if the specific heat of water is4200 J/ kg C°?

Given:

m= 500 g =0.5kg c = 4200 J/kg C°∆T = 100°C - 20°C = 80 C°Question: Q = …?Answer:

Q = m x c x ∆T= 0.5 kg x 4200 J/kgC° x 80 C°= 168,000 J

So the heat received by the water is 168,000 J

10

Notes:C = Heat capacity (J/C°)m = mass (kg)Q = heat received or released (Joules)c = specific heat capacity (J/kg C°)∆T = changes of temperature (C°)

C = m×cQ

∆TC =

Heat Capacity (C)

The heat capacity of a substance is defined asthe amount of heat required to raise its temperatureby 1 C°

Unit of Heat capacity is Joules per Celsius degree (J/C °)Heat capacity can be calculated using the following equations.

Problems of Heat and the change of temperature

Answer these following questions!1. Two containers of the same size are filled with water and sand

respectively. If they are exposed to the sun heat, which one getshotter more quickly? Why?

2. You’re heating a 3.0 kg glass block, specific heat capacity of 840J/(kg.C °), raising its temperature by 60C°. What heat do you haveto apply?

3. 2 kg of iron is heated from 15 °C to 30°C. If the heat required is13,500 J, what is specific heat capacity of iron?

4. 42 kilojoules of heat released from the 2 kg of ice at temperatures -15 ° C. What is the temperature finally, if the specific heat of iceis 2100 J/kg. C°

5. To raise the temperature of an object from 10°C to 40°C, itrequired heat 60,000 J. Calculate the heat capacity of its object!

12

Heat and the change State of Matter• When a matter change its state, the

temperature does not increase although theheat is continuously given.

• The heat is used to changing the state of matter.• The heat used for changing the state of matter is

calledLatent heat.

13

STATES OF MATTERSOLIDS

•Particles of solids are tightly packed, vibrating about a fixed position.

•Solids have a definite shape and a definite volume.

Heat

STATES OF MATTERLIQUID

Particles of liquids are tightly packed, but are far enough apart to slide over one another.

Liquids have an indefinite shape and a definite volume. Heat

STATES OF MATTERGAS

Particles of gases are very far apart and move freely.

Gases have an indefinite shape and an indefinite volume. Heat

PHASE CHANGESDescription of Phase Change

Term for Phase Change

Heat Movement DuringPhase Change

Solid to liquid

MeltingHeat goes into the solid as it melts.

Liquid to solid

FreezingHeat leaves the liquid as it freezes.

PHASE CHANGESDescription of Phase Change

Term for Phase Change

Heat Movement During Phase Change

Liquid to gas

Vaporization, which includes boiling and evaporation

Heat goes into the liquid as it vaporizes.

Gas to liquid Condensation Heat leaves the gas as it condenses.

Solid to gas Sublimation Heat goes into the solid as it sublimates.

Melting and Freezing• Melting point is the temperature

when a matter is starting to melt.

Example: melting point of ice is 0°C

• Freezing point is the temperature

when a matter is starting to freeze.

Example: freezing point of water is 0°C

Melting point = Freezing point

14

Meltingpoint

15Melting heat and Freezing heat

The amount of heat absorbed by every 1 kg of matter formelting at its melting point is called Melting heat (L).

The amount of heat released by 1 kg of matter for freezing atits freezing point is called Freezing heat (L).

SI Unit of Melting Heat and Freezing Heat: J/kg

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AMOUNT OF HEAT (Q) RECEIVED OR RELEASED BY A MATTER

WHEN IT MELTS OR FREEZES

Where:Q = amount of Heat received or released (J)m = mass of matter (kg)L = Melting heat or Freezing Heat (J/kg)

17

Boilingpoint

boiling and condensation PointBoiling point is the temperature when a matter is

starting to boils.Example: boiling point of water is 100ºCCondensation point is the temperature when a

matter is starting to condenses.Boling point = Condensation point

Boiling point of a liquid is affected by airpressure

• The greater the air pressure the greater theboiling point of liquid

• On the sea level, at air pressure of 1 atm, theboiling point of water is 100 º C.

• At higher place, the air pressure is decreaseand boiling point of water is also decrease.

18Vaporing heat and condensation heat

The amount of heat absorbed by every 1 kg of matter forvaporize at its boiling point is called vapouring heat (U).

The amount of heat released by 1 kg of matter for condenseat its condensation point is called condensation heat (U).

SI Unit of Vapouring Heat of Condensation Heat: J/kg

19

AMOUNT OF HEAT (Q) RECEIVED OR RELEASED BY A MATTER

WHEN IT EVAPORATES OR CONDENSES

Where:Q = amount of Heat received or released (J)m = mass of matter (kg)L = Vaporing Heat or Condensation Heat (J/kg)

Substance Meltingpoint(ºC)

MeltingHeat(J/kg)

Boilingpoint

(ºC)

VapouringHeat(J/kg)

Helium -269,65 35,23x10

-268,93 42,09x10

Nitrogen -209,97 42,25x10

-195,81 52,01x10

Oxygen -218,79 41,38x10

-182,97 52,13x10

Ethylalcohol -114 51,04x10

78 58,54x10

Water 0 53,33x10

100 62,26x10

Sulfur 119 43,81x10

444,6 53,26x10

Lead 327,3 42,45x10

1750 58,70x10

Aluminum 660 53,97x10

2450 71,14x10

Silver 960,8 48,82x10

2193 62,33x10

Gold 1063 51,34x10

2660 61,58x10

Copper 1083 35,23x10

1187 65,06x10

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No Evaporation Boiling

1. Occursatanytemperaturebelowboilingpoint

Occursatafixedtemperature(boilingpoint)

2. Occursontheliquid’ssurface Occursthroughouttheliquid

3 Nobubblesareformed Bubblesareformedintheliquid

4 SlowProcess Quickprocess

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Differences betweenevaporation and boiling Point

22

• Heating– When we heated liquid, the molecules near the surface vibrate

faster, which enable them to release from liquid’s surface

• Blowing air through the liquid’s surface– If we blow air through the surface of a hot water, the air near the

water surface would carry the water’s molecules at the surface.• Extending the surface

– To make hot tea in a cup cold faster, you should pour on a saucer,because the surface area of the saucer is larger than on the cup,so the molecules have more chances to leave the water surface

• Decreasing the pressure on the surface– If the pressure decreasing, the space between air molecules near

the surface become looser and it make easier for the molecules ofwater to fill the empty space among the molecules of air.

Several Aspect That Speed up Evaporation

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1. If ice melting, the state change from …. to …2. For melting, ice …. heat energy3. During ice melted, temperature is….. and it is

called …4. Amount of heat energy used to melt you can

calculate with the formula5. During the water boil, the temperature is … and

it is called …6. During the water boil, the state change from …

become … and is called …7. During evaporation the water ……heat energy.8. Quantity heat energy used to evaporation can

calculate by the formula …

Quick Quiz!

Example24

1. Calculate the quantity of heat required to melt 3 kg of iceon 0ºC ! (L = 3.36 x 105 J/kg)

Answer:

Q = 3 kg x 336,000 J/kgQ = 1,008,000 J = 1,008 kJ

Known: m= 3 kgL = 3.36 x 105 J/kg = 336,000 J/kg

Question: Q ?

Q=mxL

25Example

2. Calculate the quantity of heat required to change 500 gramsof water at a temperature of 100ºC into water vapor at atemperature of 100ºC! (U = 2270 kJ/kg)Known: m= 500 grams = 0.5 kg

U = 2270 kJ/kg

Question: Q ?Answer:

Q=mxU

Q = 0.5 kg x 2,270 kJ/kg

Q = 1,135 kJQ = 1,135,000 J

and vapouring heat of water is 2270 kJ/kg)

26

Example3. Calculate the heat required to change 1 kg of water at

temperature of 80ºC into 1 kg of water vapor at atemperature of 100ºC (specific heat of water is 4200 J/kgºC

Known: m= 1 kg∆T = (100-80) Cº = 20 Cº 100ºCc = 4200 J/kg CºU = 2270 kJ/kg = 2,270,000 J/kg 80ºC

Question: Q totalAnswer:

Temperature

Heat(J)Q2 = m x UQ1 = m x c x ∆T

Q1

Q2

Q total = Q 1 + Q 2

=(m x c x ∆T) + (m x U)=(1 kg x 4200 J/kg Cº x 20 Cº)+(1 kg x 2,270,000J/kg)

= 84,000 J + 2,270,000 J = 2,354,000 J

Answer:

Example27

4. Ice cube has mass 100 gram at 0ºC. If it heated until 20ºCthe all ice become water. How much heat energy absorb?(melting heat of ice = 80 cal/g ; specific heat of water 1 cal/g cº)

Known: m= 100 g∆T = (20-0) Cº = 20 CºL = 80 cal/gc = 1 cal/gCº

Question: Q total

Q2 = m x c x ∆TQ1 = m x L

Q total = Q 1 + Q 2

= (m x L) + (m x c x ∆T)=(100 g x 80 cal/g ) + (100 g x 1 cal/g C ºx 20 Cº )= 8,000 cal + 2000 cal= 10,000 cal

28

Exercise of Heat

1. Calculate heat needed to change 100 gram of ice at – 30°C intowater vapor at 120°C.

cice = 2100 J/kg°Ccwater = 4200 J/kg°Ccwater vapor = 2010 J/kg°CLice = 336,000 J/kgUwater= 2,270,000 J/kg

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• Joseph Black (16 April 1728 – 6December 1799) was a Scottishphysician, known for hisdiscoveries of latent heat, specificheat, and carbon dioxide.

Who Is Black?

30

• When two substances or more are mixed, theamount of heat released by the substancewith higher temperature is equal to theamount of heat absorbed by the substancewith lower temperature.

•Q released = Q received

The Black Principle

Qreleased= Q received

m1. cwater . ∆T1 = m2. cwater . ∆T2

m1. cwater . (T1 – Tf) = m2. cwater . (Tf – T2)m1. (T1 – Tf) = m2. (Tf – T2)

100 g(40 – Tf) = 200 g. (Tf – 10)4000 – 100Tf = 200 Tf – 20004000+2000 = 200 Tf+ 100 Tf

6000 = 300 Tf

Tf = 6000/300 = 20°C

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100 grams of hot water at 40°C is mixed with 200 grams of water at10°C . What is the final temperature of this mixture?Given: m1= 100 grams T1= 40°C

T2 = 10°Cm2 = 200 gramsQuestion: Tf (Final Temperature)Solution

Example

Tf

T1

T2

∆T1 = T1 - Tf

∆T2 = Tf – T2

1. The volume of water in glass B is half of the volume ofwater in glass A. The water is then mixed in glass C. Thefinal temperature of the water in glass C is…

2. ½ kg of hot water at 80°C is mixed with 2 kg of coldwater. What is the temperature of cold water if the finaltemperature of mixture is 24°C?

32Exercise Of Black Principle

THANKS!